Jack Osbourne: How I Discovered I Have Multiple Sclerosis

Jack Osbourne knew something was wrong last month when his vision was failing him.

"I couldn't see anything in front of me," Osbourne, 26, tells PEOPLE in this week's cover story. But when he sought medical help for that problem, he received a shocking diagnosis.

Multiple sclerosis was to blame for his vision loss – 80 percent in his right eye. He's now beginning medication and adopting a healthier diet regimen to help reduce symptoms of the disease, which attacks the brain and spinal cord and can affect vision, movement and cognition. And luckily, his vision has also improved. "It's just one of those things you take as it comes," says Jack. "It's all about your outlook."

Just weeks after receiving the news, Jack and his mother Sharon opened up in an emotional interview with PEOPLE at Jack's parents' home. Says Sharon: "The first thing Ozzy and I asked ourselves was, 'What did we do wrong?' "